Downhole fuel cell with steam adsorption and pressure compensation

ABSTRACT

A fuel cell for use in downhole applications stores steam created by the chemical reaction in a desiccant like Zeolite. The fuel cell also uses ambient hydrostatic pressure to increase cell voltage and power-density.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/920,623, filed Jun. 18, 2013, the entire disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure is related to fuel cells.

2. Background of the Art

Fuel cells make use of an electrochemical reaction involving a fuel andan oxidant in a cell that comprises an anode, cathode, and electrolyte,to generate electricity without also generating the unwanted by-productsassociated with combustion, while providing relatively higher energyefficiency. Thus, fuel cells potentially have a number of advantagesover other power generation or storage means in many applications. Anumber of obstacles have hindered the use of fuel cells in high powerand/or long term downhole applications. For instance, the reactionproduct, typically water, needs to be removed from the fuel cell stackin order to continuously run the fuel cell. Removal of the waterdownhole presents a challenge because the surrounding pressure iscommonly higher than that present in a conventional fuel cell placed atsurface in an ambient environment and operating in air.

The present disclosure addresses this and other challenges for use offuel cells in wellbore environments.

SUMMARY OF THE DISCLOSURE

In some aspects, the present disclosure relates to a wellbore apparatusthat may include a downhole tool conveyed into the wellbore with aconveyance device; a fuel cell associated with the downhole tool; and adesiccant receiving a fluid byproduct produced by the fuel cell.

In aspects, the present disclosure relates to a wellbore apparatus thatmay include a downhole tool configured to be conveyed into the wellborewith a conveyance device; a fuel cell associated with the downhole tool;and a pressure applicator increasing a hydrostatic pressure applied tothe fuel cell.

Examples of certain features of the disclosure have been summarizedrather broadly in order that the detailed description thereof thatfollows may be better understood and in order that the contributionsthey represent to the art may be appreciated. There are, of course,additional features of the disclosure that will be described hereinafterand which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed understanding of the present disclosure, reference shouldbe made to the following detailed description of the embodiments, takenin conjunction with the accompanying drawings, in which like elementshave been given like numerals, wherein:

FIG. 1 is a schematic diagram of an exemplary drilling system fordrilling a wellbore using a fuel cell arrangement according to thepresent disclosure; and

FIG. 2 shows one embodiment of a fuel cell with water sorption deviceand pressure compensation device according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIG. 1, there is schematically illustrated a drillingsystem 10 for forming a wellbore 12 in an earthen formation 13. While aland-based rig is shown, these concepts and the methods are equallyapplicable to offshore drilling systems. Also, the wellbore 12 mayinclude vertical sections, deviated sections, and horizontal sections,as well as branch wellbores. The drilling system 10 may use a bottomholeassembly (BHA) 14 conveyed by a rigid wellbore conveyance device such asa drill string 16 suspended from a rig 18. The drill string 16 mayinclude a drill bit 20 at a distal end. The drill string 16 may includeany known drilling tubular adapted for use in a wellbore, e.g., jointeddrill pipe, coiled tubing, casing, liner, etc.

The BHA 14 can also contain directional sensors and formation evaluationsensors or devices (also referred to as measurement-while-drilling,“MWD,” or logging-while-drilling, “LWD,” sensors) determiningresistivity, density, porosity, permeability, acoustic properties,nuclear-magnetic resonance properties, corrosive properties of thefluids or formation downhole, salt or saline content, and other selectedproperties of the formation 13 surrounding the BHA 14. The BHA 14 canfurther include a variety of other sensors and communication devices 24for controlling and/or determining one or more functions and propertiesof the BHA (such as velocity, vibration, bending moment, acceleration,oscillations, whirl, stick-slip, etc.) and drilling operatingparameters, such as weight-on-bit, fluid flow rate, pressure,temperature, rate of penetration, azimuth, tool face, drill bitrotation, etc. A suitable telemetry sub 26 using, for example, two-waytelemetry, is also provided as illustrated in the BHA 14 and providesinformation from the various sensors and to the surface. The bottomholeassembly 14 can also include one or more fuel cells 50 configured tosupply electrical energy to the various electronic or sensor componentsof the BHA 14.

Although the fuel cells 50 disclosed herein is discussed with respect tothe exemplary drilling system 10 of FIG. 1, alternate embodimentswherein the fuel cell 50 is incorporated into a tool conveyed by anon-rigid conveyance device such as a wireline, slickline, e-line, orcoiled tubing, is also considered within the scope of the presentdisclosure.

Turning now to FIG. 2, there is schematically shown one embodiment of afuel cell 50 according to the present disclosure that may be used with aBHA 14 in a wellbore 12. In a fuel cell 50, electrical energy is createdby a catalytic oxidation of hydrogen. The chemical reaction can be seenas a reverse reaction to the electrolytic decomposition of water.

The fuel cell 50 may include two electrodes, an anode 62 and a cathode64, that are separated by an electrolyte 66. The anode 62 receives aflow of hydrogen 30 and the cathode 64 receives a flow of an oxidant 32,such as oxygen. Gas diffusion layers 68 may be used to separate theelectrolyte 66 from the electrodes 62, 64. At the anode 62, hydrogenatoms are separated into protons and electrons. While the protonsdiffuse through the electrolyte 66 to the cathode 64, the electrons haveto travel via an outside electrical circuit 70 to the anode 62. At theanode 62, protons and electrons form hydrogen again and react withoxygen to produce a fluid byproduct, such as water 72, at the cathode64. The byproduct may be gaseous water or liquid water.

For optimal operation of the fuel cell 50, the water 72 (e.g., waterdroplets) should be removed from the surface 74 of the cathode 64.Embodiments of the present disclosure include a water sorption device 80for storing the water 72. The water sorption device 80 may use eitheradsorption or absorption for water removal. Adsorption is the adhesionof atoms, ions, or molecules from a gas, liquid, or dissolved solid to asurface. Absorption occurs when a fluid permeates a solid.

In one arrangement, the water sorption device 80 may be configured touse an adsorption process to store the water 72 in a solid media 82. Onesuitable desiccant for the solid media 82 is Zeolite. Zeolite can beformed to store up to 25% water under downhole conditions. In someembodiments, the pressure is controlled so that the vapor pressure ofsteam that is in contact with Zeolite is relatively low. However, thepresent disclosure is not limited to any particular type of desiccant.In such embodiments, the surface 74 of cathode 64 may be directedpassively, i.e., without use of additional components.

As shown the solid media 82 may be disposed in an enclosure 84 that alsoencloses the fuel cell 50. Thus, the water 72, which is in the form of agas (i.e., water vapor or steam), may flow to and into the solid media82. In other embodiments, the solid media 82 may be disposed in aseparate enclosure (not shown). Also, while natural diffusion may beused to transport the water 72 to the solid media 82. In otherembodiments, devices that control temperature or some other parametermay be used to actively move the water 72. In either instance, thesurface 74 of the cathode 64 is kept in a substantially dry condition.The term “substantially” generally means that the cathode 64 is dryenough such that the fuel cell 50 can continue to generate electricalenergy.

In another aspect, the fuel cell 50 may use a controlled pressure toenhance fuel cell voltage and power. In one arrangement, the fuel cell50 may include a pressure applicator 90 that can vary (e.g., increase ordecrease) a pressure applied to the fuel cell 50 and to the in-flowinggases 30, 32. The pressure applicator 90 may include a passage 92 thatis in fluid communication with a wellbore fluid (not shown) surroundingthe BHA 14. In some arrangements, the pressure applicator 90 may beconfigured to apply all or a portion of the hydrostatic pressure of thesurrounding wellbore fluid to the fuel cell 50. A compensator 94 may bepositioned along the passage 92 that converts or transforms thehydrostatic pressure of the wellbore fluid in the passage 92 of asuitable conduit such as a probe or tube into a pressure that is appliedto an interior 96 of the fuel cell 50 or to individual features, such asthe electrodes 62, 64. The compensator 94 may use known devices forcontrolling fluid flow such as valves, valve actuators, throttles, andclosed hydraulic fluid systems. The compensator 94 may also use knownmechanisms such as variable volume pistons-cylinder arrangements orbladders that can communicate pressure while isolating the interior 96from the wellbore fluid (not shown) in the passage 92. In someembodiments, a controller 98 may be used to adjust the amount ofpressure applied to the fuel cell 50.

In other embodiments, the pressure may be applied using a downholepressure source (e.g., a compressed gas or biasing element such as aspring). That is, the pressure applicator may use an onboard artificialpressure source as opposed to a naturally occurring pressure source.

While the foregoing disclosure is directed to the one mode embodimentsof the disclosure, various modifications will be apparent to thoseskilled in the art. For example, while the fuel cell 50 is shown withboth a water sorption device and a pressure applicator, a fuel cell 50may use one of these two features. It is intended that all variationswithin the scope of the appended claims be embraced by the foregoingdisclosure.

1-5. (canceled)
 6. An apparatus for use in a wellbore having a wellborefluid at a hydrostatic pressure, comprising: a downhole tool configuredto be conveyed into the wellbore with a conveyance device; a fuel cellassociated with the downhole tool; and a pressure applicator increasinga hydrostatic pressure applied to the fuel cell and thereby increasing afuel efficiency of the fuel cell.
 7. The apparatus of claim 6, whereinthe pressure applicator communicates at least a portion of thehydrostatic pressure to the fuel cell via a passage in communicationwith the wellbore fluid surrounding the downhole tool.
 8. The apparatusof claim 6, wherein the hydrostatic pressure is applied to at least onefluid fed to the fuel cell.
 9. The apparatus of claim 8, the at leastone fluid is one of: (i) hydrogen, and (ii) oxygen.
 10. The apparatus ofclaim 6, wherein the pressure applicator is configured to increase thehydrostatic pressure to a predetermined maximum pressure. 11-15.(canceled)
 16. A method for use in a wellbore having a wellbore fluid ata hydrostatic pressure, comprising: conveying a downhole tool into thewellbore with a conveyance device, the downhole tool having anassociated fuel cell; and increasing a hydrostatic pressure to the fuelcell using a pressure applicator and thereby increasing a fuelefficiency of the associated fuel cell.
 17. The method of claim 16,wherein the pressure applicator communicates at least a portion of thehydrostatic pressure to the fuel cell via a passage in communicationwith the wellbore fluid surrounding the downhole tool.
 18. The method ofclaim 16, wherein the hydrostatic pressure is applied to at least onefluid fed to the fuel cell.
 19. The method of claim 18, the at least onefluid is one of: (i) hydrogen, and (ii) oxygen.
 20. The method of claim16, wherein the pressure applicator is configured to increase thehydrostatic pressure to a predetermined maximum pressure.